Question 8: Which of the following statements is correct regarding the propagation of light of different colours of white light in air?
Answer: (c) All the colours of white light move with the same speed
Explanation: Speed of light is constant in a given medium
Question 9: The danger signals installed at the top of tall buildings are red in colour. These can be easily seen from a distance because among all other colours, the red light
Answer: (b) Is scattered the least by smoke or fog
Explanation: As you have seen in explanations to questions 7, the wavelength of red light is the maximum among all colours of visible spectrum. Due to this, red light is scattered the least by smoke or fog and is easily visible from a distance.
Question 10: Which of the following phenomena contributes significantly to the reddish appearance of the sun at sunrise or sunset?
Answer: (b) Scattering of light
Explanation: During morning and evening, light has to travel a longer distance compared to any other time of the day. While travelling a longer distance, colours at the blue end of the visible spectrum get scattered away. Due to this, only colours at the red end of the spectrum reach our eyes and the sun appears reddish at sunrise or sunset.
Question 11: The bluish colour of water in deep sea is due to
Answer: (c) Scattering of light
Question 12: When light rays enter the eye, most of the refraction occurs at the
Answer: (b) Outer surface of the cornea
Question 13: The focal length of the eye lens increases when eye muscles
Answer: (a) Are relaxed and lens becomes thinner
Explanation: When ciliary muscles are relaxed, then lens becomes thinner and its focal length increases. When ciliary muscles contract, then lens becomes thicker and its focal length decreases.
Question 14: Which of the following statements is correct?
Answer: (c) A person with myopia can see nearby objects clearly
Explanation: Myopia is also called far-sightedness in which a person cannot see distant object clearly, but can clearly see nearby object.
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